Arc welding system



H. L. MILLS ARC WELDING SYSTEM Filed Oct. 11. 1937 May 14, 1940.

2 Sheets-Sheet l 4 w m. 1! 7 M 1 w &1 m M ll 2 1) 7 n u Q m. 1 2 Z Z O w z 2 1w 2) 5 M H 2 w Wm m A mb U W m 3 M WW6 1 11 7 1 L w 5 m 6 9 w n HQ w .m j w m b M My May 14, 1940. I Ls 2,200,632

ARC WELDING SYSTEM Filed Oct. 11-. 1937 2 Sheets-Sheet 2 Voltage Across Arc 5i 5m 3%4 455 5M pm a H 59 457 I 544 I 552 Henry L. M1119,

TATES PATENT OFFICE Henry L. Mills, Minneapolis, Minn, assignor to Guy L. Pugh, Minneapolis, Minn.

Application October 11, 1937, Serial No. 168,411

2 Claims. (01. 171-419) and has for an object to provide an arc welding current line 12' having leads I3 and E4. The system which is extremely practical in operalead i3 is directly connected to the primary H tion and highly efficient. while the lead i4 is connected to a special form 5 Another object of the invention resides in proof reactance l5 which will be presently more fully 5 viding an arc welding system by means of which described. A conductor [6 connects this reactdiiierent values of current may be procured withance with the other side of the primary II. The out the use of taps on the welding transformer. secondary circuit of the welding transformer l0 Another object of the invention resides in procomprises two conductors i1 and I8 of which 10 viding an arc welding system in which practicalthe conductor I8 is connected to the work which 10 ly constant current delivery is procured at the is to be welded and which is indicated by the load regardless of the arc voltage. reference numeral E9. The conductor i! is con- A still further object of the invention resides nected to the electrode which is designated at in providing an arc welding system for use with 2i and which may be a welding rod iurnishing alternating current in which a flat top wave the metal for procuring the weld and supported 15 form results. in a suitable holder, or which may be any of the Another object of the invention resides in proother ordinary forms of electrodes now in use. viding an arc welding system in which control The reactance i5 comprises a core 22 which is of the current may be procured with a'minimum constructed with three legs 23, 24 and 25, all conloss of power. nected to gather through end core members it A still further object of the invention resides and 21. On the legs 23 and 25 of core 22 are in providing an arc welding system in which conprovided windings 2t and 29 which are connected trol of the current at the load may be procured in parallel and to the lead M of the line H and from a remote locality and by a small rheostat the conductor I6 so that these two windings in as capable of being carried on the electrode holder. parallel are connected in series with the primary 25 Another object of the invention resides in proll of transformer ill. Upon the center leg 24 viding an electric welding system in which the of core 22 is provided another winding 3! which voltage at the instant of striking the arc is suiis supplied with direct current. ficiently high so that positive action results and For the purpose of energizing the winding ii 30- which immediately becomes reduced to normal two full wave thermionic rectifier tubes 32 and 30 once the arc has been struck. 33 are employed. The tube 32 comprises a fila" Other objects of the invention reside in the ment 34 and two plates 35 and 36. The tube 33 novel combination and arrangement of parts similarly comprises a filament 31 and two plates and in the details of construction hereinafter 38 and 39. These tubes are energized by means 35 illustrated and/or described. of a transformer 4| which comprises a primary 35 In carrying out my objects I utilize a reactance 42 and a secondary 43. These various parts are consisting of a core having a winding thereon connected as follows. The primary 42 of trans connected in series with one of the windings of former M is connected by means of a conductor the welding transformer and having another 44 to a variable resistance #5. This resistance winding which is supplied with direct current. is connected by means of a conductor 46 to the 40 In the drawings: lead it of line it. The other side of primary M Fig. i is a wiring diagram of an arc welding of transformer M is connected by means of consystem illustrated in the embodiment of my in ductor 41 to an ammeter 48 which in turn is vention. connected by a conductor 4. to the lead l4 of line .15 Fig. 2 is a wiring diagram of a modification of it. The secondary 43 of transformer 4| is prothe invention. vided with a center tap 5| which is connected by Fig. 3 is a wiring diagram of still another form means of a conductor 52 with one end of the of the invention. winding 3i on the center leg 24 of the reactance Fig. 4 is a diagrammatic view of a number of i5. One end of the secondary 43 is connected so curves showing the performance of my improved by conductors 53, 54 and 55 to the two plates arc welding system as compared with other sys- 35 and 38 of rectifier tubes 32 and 33. The terns. other end of the secondary 43 is connected by My invention, as shown in Fig. 1, comprises a means of conductors 56, 5'! and 58 to the other main arc welding transformer iii which is proplates 36 and 39 of the two rectifier tubes 32 .55 videcl with a primary ii and a secondary i2. and 33; The other side of the winding 3.| of re- My invention relates to arc welding systems The primary H is energized from an alternating actance i5 is connected by means of a conductor 59 with corresponding sides of the two file. ments 34 and 31 of the two tubes 32 and 33. It will readily be comprehended that, when the filaments 34 and 3'! of said tubes are properly heated, direct current will be furnished to the winding 31 through the conductors 52 and 59.

For the purpose of heating the filaments 34 and 3'5 of the two rectifier tubes 32 and 33, a transformer, such as indicated at 5!, is employed. This transformer comprises a primary 62 and a split secondary having two sections 63 and 64. The section 63 is connected by means of conductors and 65 to the filament 35 of tube 32 while the secondary section 64 is similarly connected by means of conductors 61 and 63 to the filament 37! of tube 33. .The primary iii? of transformer til is connected by means of two conductors 69 and "H to the two leads i3 and M of line 12'.-

In the wiring diagrams illustrating my invention I have not shown any switches or other means for making and breaking the various circults oi the invention. It can, however, be readminimum.

ily comprehended that switches may be inserted in any oi the circuits illustrated and wherever found desirable.

The operation of my invention is as follows. If enough direct current is passed through the winding M. to saturate the core 22 then, when the weldingsystem is in operation, the flux pro duced by the-alternating current flowing through windings 28 29 is ineffective and the impedance in the primary circuit is reduced to a v A maximum amount of current can thus flow through the electrode 2! and the work i9. lithe direct current; passing through wincling 3l-', is reduced to a minimum then the flux produced by windings 28 and 125i alternates in core 22 in accordance with the frequency and wave form oi": the current in primary ll of transformer iii which greatly increases the impedance oi. reactance l5 and limits the amount oi current flowing through the electrode 2| and work l9. In this manner it is possible to vary the out put of the transformer it and to procure any desired current at the arc by merely varying the direct current supplied to the winding 3i. This is accomplished in this particular instance by varying the resistance which controls the input to transformer M and which in accordance with the customary behavior of rectifier tu'bes, controls the direct current out-put from fthe same.

With such tubes the heating of the filaments re-- mains constant and merely the voltage across the plates is varied to procurethe "desired variation in direct current out-put'.] I

In the operation of the transformer. the operator selects the desired current which he wishes to. use at the arc and adjusts the variable resistance Mi until the arnmcter 18 shows the proper setting. Ammeter may be calibrated to read directly in ampcres, the current flowing in the welding arc at the work.

Since no current is flowing in the windings 2E and 29 before the arc is struck, the voltage acrossjthc electrode 28 and the worl; if) is a maximum. This insures positive striking-of the arc. As soon as the arc is struck, current flows through the secondary i2 and primary ll oi. transformer Ml which likewise flows through the windings and fill of reactance it. This incr ases the impedance of the said reactzr.:c which. immediately cuts down the voltage of the transformer and likewise the amount of current ilmving through the electrode and the work. It will thus readily be apparent that the system automatically cuts down the current once the arc has been. struclr.

In Fig. 4 l have shown some curves wluch illustrate the performance of my improved welding system in comparison with the ordinary type of welding systems now in use. These curves plotted with current values at the arc as ordinates and with voltages across the arc as ab scissas. The two sets of curves illustrated have been taken for 170 amperes and for 8G amperes. The curves were procured from actual tests, all using the same welding transformer. Curve it shows the performance of a welding system cinbodying the instant invention with current of 170 15 amperes. Curve "M shows a welding system in which an ordinary reactance, not utilizing a direct current winding is employed for regulating the current at the arc. Curve l5 shows the performance of the same transformer when a practically non-inductive resistance is used for controlling the current at the arc. Inasmuch as the voltage at the arc is a function of the length of the arc, it will readily be comprehended that, if the curves were straight horizontal lines, the same amountoi current would flow regardless of the length of the arc. This would enable the operator to procure the same flow of metal whether he maintained a long or a short are thereby enabling the operator to produce better work with less accuracy in maintaining a certain length of arc. From an observation of the three curves it will be found that curve 13, which shows the performance of the instant invention, comes the closest to being a horizontal line. Curves iii-o, :1.

IL-11, and l5a correspond to it, "Hi and iii and illustrate the variation in voltage when the system is regulated to produce a current of B0 amperes at the arc. These curves are quite similar tothe curves previously referred to, excepting that the variation between the three curves is less as the voltage increases. It will thus become apparent that for greater currents the instant invention becomes more efficient which greatly assists in making large welds where it 45 becomes difficult to maintain the exact length of arc. It will readily become apparent that with my invention greatly improved results are obtaincd over and above systems using an ordinary type of reactance or non-inductive resistance.

In Fig. 2 I have shown a modification of the invention where the reactance is placed in the secondary circuit and in which plate rectifiers, such as copper oxide plate rectiflers, are used in place of the thermionic tubes. In this form of 5: the invention another type of control for the direct current has been illustrated. Since certain of the elements in this form of invention are identical with those shown in Fig. i, the descripwill tion thereof will not be repeated and similar ref to erence numerals preceded by the digit 1 will be used to indicate corresponding par-ts.

As in the case or the form of the shown in Fig. l. the windings iilfii if he reactance i iii are connected to the conductor E cs leading from the secondary N2 of transformer ill'i. These windings are further connected by means of a conductor H5 with the work lial so that the said windings are in series with the transformer secondary H2 and the In place of the two thermionic ti a bridge rectifier i'll'l is utilized. *Ihis rec comprises four plate rect'liicrs illl, ii" i which are connected together by .he... conductors W3 l l l. tw

ductors it? and ltd leading from the winding iiil of reactance M are connected to the two conductors iiill and i953 of the bridge. The other two conductors B92 and W4 of the bridge are connected by means or conductors B95 and M6 to the secondary liili of transformer its. The primary tilt of this transformer is connected to the leads H3 and lid of line H2 through another reactance Ml which will now be described in detail. v

The reactance 2M is similar to the reactance iii and is constructed with a core 202 having three legs 2G3, 2M and 205. These legs are connected together by means of end core members tilt and EM. On the legs and 205 are alternating current windings 2M and 209, while on the center leg 204 is a direct current winding 2H. The two windings tilt and 209 are connected together in parallel through conductors M2 and 293 which in turn are connected through a conductor 2M with one side of the primary I99 of transformer Hill. The other ends of these windings are connected together by means of conductors tilt and Zlt, which in turn, are connected by means of a conductor 2H to the lead N3 of line M2. The other end of the primary i199 of transformer tilt is connected by means of a conductor 208 to the other lead N4 of line H2.

One end of the winding Ell is connected by means of a conductor 2m with a variable resistance iiil, which in turn is connected by means of conductor 222 to the conductor iill of the bridge rectifier ii'fl. winding Jl l is connected by means of a conductor to an ammeter 223, which in turn is connected by means of conductor 224 to the conductor ltd of the bridge rectifier l'lli. By means of the circuit containing .these last named conductors direct current is supplied to the winding The method of operation of the reactance 2M is the same as the reactance -i it. When the core is saturated by the flux produced by the direct current flowing in the winding 2i i, the impedance oi the reactance is a minimum and a large amount of direct current is supplied by the bridge rectifier lit to the winding Hi. When the direct current in the winding 2H is reduced through the variable resistance 2211, the impedance of the reactance 2M greatly increases and the direct current supplied by bridge rectifier Fill decreases. Thus the current flowing in resistance 22% is small so that an extremely small resistance may be used. I have found by experiments that a small resistance, capable of being carried on the electrode holder of the arc welding system, may be conveniently employed whereby variation in the welding current within the entire range of the welder may be procured. Also ammeter 223 may be sufficiently small to be carried on the electrode holder.

In Fig. 3 I have shown still another modification of the invention which is similar to that shown in Fig. 2, and in which certain of the elements are identical. The description of these elements will not be repeated and the same reference numerals having a first digit 3 instead of 1 will be used to designate corresponding parts.

In the form of the invention shown in Fig. 3, two banks of rectifiers 428 and 426a are utilized. The bank 6% consists of eight plate rectifiers 427, d228, 8253, M21433, did. The rectifiers iii, 12%, Q29 and idd are connected to the rectiflers and 434 by means of conductors The two rectifiers Hi and 135, 4535, 137i and The other end of the 428 are connected together by means of a conductor 439. The rectiflers 429 and 43B are connected together by means of a conductor 44!. The two rectifiers 43! and 432 are connected by means of a conductor 442, while the rectifiers 433 and 434 are connected by means of a conductor 443. Conductors 439 and 44H are connected together by means of a conductor 444, while conductors 442 and 443 are connected together by means of a conductor 445.

For energizing the bank of rectifiers 426 a transformer 44E is utilized. This transformer comprises a primary 441 and a secondary 448. One end of the secondary 448 of transformer 446 is connected by means of a conductor 458 to both the conductors 435 and 436. The other end of the secondary 448 of this transformer is connected by means of a conductor 452 with both of the conductors 43l and 438. The primary 441 of transformer 446 is connected by a conductor 453 to a variable resistance 454, which in turn is conn'ected by a conductor 455 to the lead 3l3 of line M2. The other side of the primary 447 of this transformer is connected by means of a conductor 456 to the lead 3l4 of line 3H2.

The bank of rectifiers 426a is constructed identically with the bank 426 and is connected up in the same manner. The description thereof will hence not be repeated. This bank includes terminal conductors 55l, 552, 544 and 545 which correspond with the conductors Mil, 452, 444 and 445 of the bank. 426. A transformer 45! is utilized for energizing the rectifiers of bank 426a. This transformer comprisese primary 455i and a secondary 459. The primary 4% of this transformer is connected by means of two conductors 4M and 462 to the conductors 455 and 456 previously referred to. By means of this circuit the two transformers M6 and 451 are connected together in parallel and are controlled by the single resistance 454. I'he center winding iii of reactance 345 is connected by means of conductors 352 and 359 to the conductors 4M and 545 respectively. Conductor 445 is connected by another conductor 463 to conductor 544. The two conductors E5! and 552, as with the bank 426 are connected to the secondary 459 of transformer 45'. The form of the invention shown in 3 diilers from that shown in Fig. 2 in that a large number of plate rectifiers have been utilized whereby an appreciable amount of current can be procured and the welder used for making large welds. The performance of the systems shown in both Figs. 2 and 3 is similar to the system shown in Fig. l and the description thereof will not be repeated.

It will become readily apparent that the special form of reactance used can be inserted either in the primary circuit or in the secondary circuit of the arc welding system. In either case, the performance is substantially the same. Although I have shown two forms of rectifiers for furnishing direct current for the reactance, it can readily be comprehended that any type of apparatus for producing direct current, such as a motor generator set, may be employed. In such case a variable resistance is placed in series with the field coil of the'generator for varying the amount of current produced thereby. If a source oi. direct current is available the same may be directly employed and the voltage thereof controlled a suitable resistance or otherwise.

In experimenting with my invention i have found that the following values used in conjunction with the various elements shown in Fig. 1 proved very satisfactory. For transformer in ll have used a core having a cross section of approximately nine square inches, with a primary consisting of two coils, each having 74 turns of '7 wire. The secondary of this transformer comprises two coils, each constructed with 41 turns. each turn consisting of three strands of 7 wire connected in parallel. For the main re actance I5 I have used a core cross section of approximately four and one half square inches. The coils 28 and 29 each consist of 54 turns each constructed with two strands of it 7 wire arranged in parallel. The winding 3| consists of 450 turns of 12 wire. Any rectifying system may be used which will produce a current of about 20 amperes.

I have ,lound that, where the particular type of reaetance illustrated has been employed, an oscillograph of the wave form shows that the wave peak is substantially horizontal and thatthe maximum flow of current continues over an exceedingly great portion of the wave cycle. With my invention lesser voltage is required at the arc so that the workman is subjected to less danger.

The advantages of my invention are manifest. By means of the system employed sufiicient voltage is available at the outset to procure positive striking of the arc. After the arc has been struck, variations in length of the are do not appreciably affect the current flowing in the are so that uniform and smooth welds are procured. Due to the resulting wave form the workmen are subjected to lesser danger and at the same time a smooth are results. With my improved system the workmen can readily vary the current at the work by merely operating the variable resistance provided instead of by changing taps on the transformer windings as has heretofore been the custom.

Changes in the specific form of my invention, as herein disclosed, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. In an arc welding system, a transformer having a primary winding and a secondary winding,a rcactance having a core formed with three legs, windings on the outer legs of the core connected in parallel with one another and in series with one of said transformer windings, another winding on the intermediate leg of the core. a rectifier connected to said last named reactor winding, a second transformer having a primary winding and a secondary winding, said secondary winding being connected to said rectifier, another reactance having a core with three legs, windings on the outer legs of said core connected to one of the windings of the second named transformer, a winding on the intermediate leg connected to said rectifier and means for vary ing the current'flowing through the last named winding of the second named reactance.

2. In an arc welding system, a transformer having a primary and a secondary winding. a saturable core variable reactor connected to one of said windings, said reactor including a winding, a circuit for energizing said winding, a sec- 0nd saturable core variable reactor controlling the supply of direct current to the winding of said first reactor and controlling the current in said circuit and means for varying the saturation of said second variable reactor.

HENRY L. MILLS.

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